Caay, Mark, and Esperanza Arugay. “On Chromatic Number and Edge-Chromatic Number of the Ottomar Graph”. American Scientific Research Journal for Engineering, Technology, and Sciences 16, no. 1 (February 7, 2016): 98–107. Accessed September 12, 2025. https://asrjetsjournal.org/American_Scientific_Journal/article/view/1255.